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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Garbage Collection in Ada
Date: 1996/10/20
Message-ID: <DzL7LK.34y@world.std.com>#1/1
X-Deja-AN: 190794894
references: <01bbb910$f1e73f60$829d6482@joy.ericsson.se>
 <dewar.845732059@merv> <199610191920401982154@dialup119-3-12.swipnet.se>
 <dewar.845809398@merv>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-10-20T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.845809398@merv>, Robert Dewar <dewar@merv.cs.nyu.edu> wrote:
>But this is, so far, a fantasy. The only kind of GC provided by standard
>implementations, at least in my experience, is proper accurate GC, that is
>of course embedded into the compiler or operating system or both.

There are some counter-examples.  Hans Boehm pointed out one case in
this thread -- a GC that conservatively scans the stack (or the top-most
stack frame) for each thread/task, which is an integral part of the
compiler system.  This is done for efficiency and/or for ease of
implementation -- given the fact that it is very difficult to do garbage
collection if you have lots of tasks that can be interrupted between any
two instructions.  If the GC can happen at any time, the GC doesn't know
much about the consistency of things on the stack.  Or in registers.

But I still share your (Robert's) nervousness about relying on
conservative GC's.  And if I were implementing a GC for a GC-friendly
language and compiler, I would probably not make it conservative.

- Bob